1. Field of the Invention
This invention relates to a connection method for conductively connecting a covered wire (conductor) to another member, and a connection structure of a covered wire.
2. Description of Related Art
Various connection modes such as a connection between a covered wire W and a terminal, a connection between at least two covered wires W, a connection between a covered wire W and a connector, etc have been hitherto utilized to conductively connect a covered wire to another member have been hitherto utilized.
With respect to the connection mode for connecting the covered wire to the terminal, a press-fitting manner, a press-contacting manner (see Japanese Examined Utility Model Application No. 60-37814), a soldering manner, an ultrasonic welding manner (see Japanese Laid-open Patent Application No. 2-106092), and other connection manners have been hitherto known.
The press-fitting connection is performed as follows. A cover portion at a connection portion of a covered wire is removed from the covered wire to expose a conductive wire portion at the connection portion.
Thereafter, the exposed conductive wire portion of the covered wire is placed on a connection portion of a terminal fitting (terminal), and then the conductive wire portion is press-fitted to the terminal fitting by crimping the conductive wire portions through a pair of conductor crimping pieces which are erectly formed at both sides of the terminal fitting so as to confront each other at the connection portion, thereby conductively connecting the covered wire to the terminal fitting. The terminal fitting is further provided with cover crimping pieces to improve a mechanical connection strength, and the conductive wire portion and the cover portion are press-fitted to the terminal fitting by the conductor crimping pieces and the cover crimping pieces.
The press-contacting connection is performed as follows. A connection portion of a covered wire is pressed into a slot of a press-contacting blade which is provided to a connection portion of a press-contacting terminal so that the cover portion of the covered wire is peeled off by the press-contacting blade, thereby conductively contacting the press-contacting blade to the conductive wire portion.
The connection using the soldering manner or the ultrasonic welding manner is performed as follows. A cover portion of a connection portion at one end portion of the covered wire is removed to exposed a conductive wire portion, and then the exposed conductive wire portion is welded to a connection portion of a terminal fitting by soldering or ultrasonic welding, thereby conductively connecting the covered wire to the terminal fitting. With respect to the connection mode for connecting two or more covered wires to one another, a connection manner using a joint terminal, a thermal press-fitting connection manner (Japanese Laid-open Patent Application No. 3-1462), etc. have been hitherto known.
The joint-terminal connection is performed as follows. Cover portions of both covered wires are removed at a connection portion thereof to expose conductive wire portions of the covered wires. These covered wires are placed so that the conductive wire portions thereof are overlapped with each other, and these conductive wire portions are crimped through a joint terminal and press-fitted to each other to conductively connect these conductive wire portions of the covered wires.
The thermal press-fitting connection is performed as follows. The cover portions of both covered wires are removed at a connection portion thereof to expose conductive wire portions of the covered wires. The exposed conductive wire portions are overlapped with each other and placed between electrodes. The overlapped conductive wire portions are supplied with current through the electrodes under pressure to heat the overlapped conductive wire portions, so that the conductive wire portions are thermally press-fitted to each other and conductively connected to each other. In addition to the above heating manner for the conductive wire portions has been known a heating manner of heating the conductive wire portions with frictional heat which is caused by ultrasonic vibration.
When the joint-terminal connection and the thermal press-fitting connection as described above are performed, an insulation material such as a tape or the like is wound around the outer periphery of the connection portion to ensure insulation of the covered wires at the connection portion.
With respect to the connection mode for connecting a covered wire to a connector, a connection manner using ultrasonic welding is known (Japanese Laid-open Patent Application No.4-61777).In the ultrasonic-welding connection, a connector comprising a lower mold and an upper mold is used. The lower mold has a groove portion and the upper mold has a projection which is engagedly insertable into the groove portion. A connection portion of a covered wire is placed on a connection portion of a conductive connection member, and then the upper mold is placed on the lower mold so that the projection of the upper mold is engagedly inserted into the groove portion of the lower mold. Thereafter, ultrasonic vibration is applied to the engaged upper and lower molds from the external to melt the cover portion of the covered wire at the connection portion, thereby conductively connecting the conductive wire portion to the conductive connection member.
The conventional connection modes as described above have the following disadvantages.
In the case where the connection between the covered wire and the terminal is performed using the press-fitting, the soldering or the ultrasonic welding, the cover portion of the covered wire is required to be removed in advance to expose the conductive wire portion at the connection portion, so that a connection work is cumbersome. On the other hand, in the case where the connection is performed using the pressure-contacting manner, the cover portion is not required to be removed, however, it is unavoidable to reduce the mechanical strength of the connection portion as compared with the press-fitting or soldering connection. Therefore, simplification of the connection work is incompatible with improvement of the mechanical strength. In the case where the connection between two covered wires is performed using the joint terminal or the thermal press-fitting, the cover portion is required to be removed like the above case, and thus the connection work is cumbersome. Furthermore, in order to facilitate the crimping work of the joint terminal and the thermal press-fitting work, it is required to remove the cover portion in a relatively broad range. Furthermore, the insulation material must be wound at the connection portion in a broader range than the removal range of the cover portion, and thus the winding range of the insulation material is relatively larger than the connection portion between the conductive wire portions of the covered wires. Therefore, flexibility of the covered wire may be deteriorated, and thus the degree of freedom of wire arrangement may be reduced. Furthermore, the thermal press-fitting connection reduces the mechanical strength of the connection portion more than the joint terminal connection.
In the case where the connection between the covered wire and the connector is performed using the ultrasonic welding, a connector having such a special shape that a groove portion and a projection are formed in a lower mold and an upper mold respectively is required, and thus this connection is not applicable to all connectors. In addition, this connection mode is not easily applicable to the connection between the covered wire and the terminal and the connection between the covered wires. That is, this connection mode is unsuitable for wide use.
In addition to the various connection modes, a connection mode for connecting a multipolar connector to plural connectors through plural covered wires has been also utilized as a special case of the connection mode for conductively connecting the covered wire and the connector. In this connection mode, in some cases the multipolar connector are equipped with some portions which functionally require a waterproof property (hereinafter referred to as "waterproof-required portions"). In this case, these portions are subjected to a waterproof treatment. On the other hand, each covered wire has various gaps therein, for example, a gap between core wires (a gap formed in the conductive wire portion) and a gap between a bundle of the core wires and a cover portion surrounding the core wires, and water or the like may flow through these gaps due to the capillary phenomenon. Accordingly, when a waterproof multipolar connector is connected to plural individual connectors through a plurality of covered wires as described above, water which invades from the connectors into the covered wires may flow through the gaps formed in the covered wires into the multipolar connector. Therefore, the multipolar connector cannot be kept in a sufficient waterproof state even if it is subjected to the waterproof treatment.
As a method of avoiding the above disadvantage, the individual connectors which are connected to the multipolar connector may be subjected to the waterproof treatment in advance. According to this method, no water flows into the covered wires, and thus the sufficient waterproof property can be kept for the waterproof-required portions of the multipolar connector. However, This method needs all the individual connectors to be subjected to the waterproof treatment even when no waterproof treatment is required for some connectors, so that all the individual connectors must be designed in complicated waterproof structure and the cost may rise up due to a cumbersome fabrication work.